This invention relates to lead assemblies for electrical devices, and more particularly to lead assemblies for semiconductive devices such as diodes.
Conventional lead assemblies for diode devices are basically comprised of a lead member of specified length having a "slug," or seal member attached thereto. Having a cross-sectional area substantially larger than the lead member, the seal member is the portion of the lead assembly which is later affixed to the diode device and encapsulated in a glass envelope. This method of affixing is most usually by soldering although other methods are possible. Another lead member, which may also have a seal member attached thereto, is joined to the other end of the device before encapsulation, forming a completed crystal diode unit. The crystal diode itself is highly sensitive to heat, thereby making its power rating dependent on the heat dissipating ability of the total unit. Most of the heat is generated within the crystal and must be conducted away primarily by the seal members, or slugs, and the lead members, which act as heat sinks.
Seal members are conventionally cylindrical in shape and it is standard practice in the industry to cut these members from copper-clad wire of nickel-iron composition. A longitudinally sectional view of this cut shows a thin "wipe" of copper across only a portion of the shear surface. This shear surface provides the mounting platform for the device itself, and having only a thin wipe of copper partially there across, substantially reduces the conductivity in this area, as well as the ability of the device to dissipate heat.
It is believed, therefore, that a seal member having a substantially uniform copper coating over its entire surface which forms the first common interface with the electrical device thus providing a secondary path of heat transfer for heat generated within the semiconductive device would be an advancement in the art.